Story
STS: Plejars are known to trick advanced civilizations into joining their empire. They first appear as benevolent beings but are very deceptive, often using holographic technology to create very realistic illusions.
STO: Plejars are known as great warriors of the Light. They will not hesitate to confront and fight any darkness which they find.
Gameplay
When playing the Plejars you can do something you could not normally do according to your alignment. STS Plejars can thus ally with advanced civilizations. STO Plejars can thus declare war on STS races/groups.